Subsurface evaluation of oil and gas reservoirs are always subject to limits imposed by data quality and availability, resources, timing and costs. As a consequence, decision making should include consideration of the risks and uncertainties associated with an evaluation of the prospects and/or reservoirs. Decision analysis methods for evaluating and communicating the risks in terms of outcomes, given some defined probability distributions, are intended to be unbiased and accurate. However, comparisons of forecast and actual outcomes for projects typically show that more projects outcomes are below the median forecast (P50) values than above, indicating that in general the input probability distributions used are inaccurate and biased.
Evaluating the potential production of hydrocarbons from an exploration prospect is important in determining the economic viability of an oil, gas or oil-gas field development scheme, An exploration prospect can include one or more subsurface structures that may or may not be hydrocarbon reservoirs. Several tools exists which assist in making such risk and uncertainty evaluations and predications of quantity and commercial viability of hydrocarbons. These tools also assist in deciding how best to develop a field and how to plan for contingencies related to the uncertainties in the knowledge of the subsurface characteristics of the field in addition to uncertainties associated with implementing a particular field development scheme.
Software tools additionally exist for assessing the difference between actual and predicted outcomes for the development of the field which allow the user to predict volumetric output but not necessarily the ability to recover hydrocarbons, or the commercial viability of a specific hydrocarbon reservoir. Such known software tools provide a single reservoir analysis without a broader understanding of risks elements of the entire prospect such as: structural integrity, reservoir quality, and amplitude of each reservoir within a prospect. Available software tools provide methods for separate analysis of risk and uncertainty associated with a single reservoir risk element. In other words, the risk and uncertainty for each reservoir risk element is analyzed separately and such methods do not account for the interrelations and dependencies between the risk elements within a petroleum system.
In reality the reservoir risk elements are interrelated and dependant on one another and need to be evaluated as a whole, on a reservoir level and eventually on a prospect level, to ensure commercial success of the hydrocarbon prospect. As used herein, the term risk and/or uncertainty element(s) means the risk and uncertainty associated with an identified subsurface characteristic of interest. Another issue with the prior art software tools is that when different tools are used for risk and uncertainty evaluations of different characteristics of a particular prospect or reservoir, each of those tools will have differing graphical user interfaces that require the geologists or petroleum engineers to use valuable time to learn how to use each of the tools.
While prior art methods are capable of measuring the uncertainty of specific risk aspects of a particular reservoir there are currently no known methods of evaluating that overall risks and uncertainties on a prospect level in an integrated environment. There is a need for an integrated environment which provides a consistent graphical user interface for both input and output that enables a user to be able to interface with mulitiple reservoir evaluation tools without having to use valuable time to learn multiple software applications. The present invention thus provides an efficient way of storing and accessing information regarding the entire petroleum system, prospect and reservoirs. Moreover, because the reservoir evaluation tools of the present invention utilize the data stored in the integrated environment, the data used for each evaluation will be consistent.
Petroleum companies evaluate hundreds of prospects around the world at any one time, improving the hydrocarbon acquisition and development success rates by accurately forecasting potential risks and uncertainty elements, even a small fraction, will save petroleum companies potentially billions of dollars. Continued widespread and variable inconsistencies between predicted reserves and field production show there is a need for methods, software tools and analyses which can assess the integrated risks and confidence of each of the hydrocarbon reservoirs and the entire prospect. The present invention is intended to address this need.